The present invention relates to a method and apparatus for separating stacked cartons and including carton denesters which receive stacks of pulp cartons such as egg cartons and which provide means for separating the bottom carton from the stack to permit it to be conveyed to a subsequent processing mechanism.
A variety of types of machines such as those used to apply printing to egg cartons are capable of handling individual cartons at high rates of speed, often in excess of 200 cartons per minute. Generally, pulp egg cartons fed to such machines are tightly stacked in an open position and in large numbers. These stacks are fed to the printing machine and must be separated by a carton denesting apparatus in order that successive cartons may be delivered individually into the carton handling means. Particular difficulties are encountered in the denesting of stacks of pulp egg cartons because of the relatively rough surfaces of such cartons and because when the cartons are stacked, they present a substantial number of opposed surfaces. The denesting operation is thus retarded because it is difficult to pull these adjacent cartons apart due to the large areas which are in sliding contact and due to the high co-efficient of friction between these surface areas due to the relatively rough pulp surfaces. The stacked pulp cartons are sometimes also subject to an expansion or contraction during storage as a result of exposure to either excess moisture or excessively dry air. Such expansion or contraction of the cartons causes the cartons comprising a stack to become even more firmly wedged together making them even more difficult to pull apart during a denesting operation.
As a result of these inherent qualities of pulp egg cartons, the prior art denesting means have failed to provide an efficient and consistent means capable of separating and feeding cartons at speeds commensurate with the efficient operating speeds of the commercially available carton handling machines such as carton printing equipment.